Cracking hydrocarbon oils



April 1944- L. DE FLOREZ ETAL 2,345,553

CRACKING HYDROCARBON OILS A Filed April 8, 1941 OUTET Luis 0e FLbnr-zzJAMES W.GRAY' INVENTORS THE/R ,1 rromvs V Patented Apr. 4, 19442,345,558 CRACKING HYDROCARBON OILS Luis de Florez, Pomfret, Conn., andJames W. Gray, Lambertville, N. J assignors to Gasoline ProductsCompany, Inc., Jersey City, N. J., .a corporation of DelawareApplication April 8, 1941, Serial No. 387,418

4 Claims.

This invention relates to the cracking of hydrocarbon oils for theproduction of gasoline or motor fuel.

The invention relates to certain novel improvements in the so-calledblack oil injection method-of cracking. In this method of cracking acondensate oil is passed through a heating coil in a furnace in whichcoil the oil is subjected tohigh cracking temperatures, while a heavystock such as a residual stock is injected into the latter portion ofthe heating coil and the resultant mixture subjected to conversion. Inthis type of operation it is desirable to subject the-condensate oil inthe first sections of the heating coil to relatively high crackingtempera-- tures so that the condensate stock may be subjected to highrates of conversion to sustain reactions resulting in a production ofhigh antik-nock gasoline. The black oil or heavy stock is injected intothe latter sections of the heating coil with the idea that the hightemperature condensate stream as well as the heat of the furnace willresult in a mixture flowing through the latter portion of the coil at atemperature suflicient to effect a cracking of the mixture including theblack oil but without coking. It-frequentls happens, however, that whenthe black oil is introduced into the high temperature stream cokingdifficulties have been encountered. It appears that when the black oilis introduced into the high temperature stream a completely homogeneousmixture is not produced immediatelywith the result that portions of theblack oil are unduly heated by the high temperature stream as well as bythe furnace and coking results.

In accordance with our invention the con densate stream undergoing hightemperature cracking is removed from the furnace or heating zone anddirected into a coil section outside-the furnace vor heating zone -towhich no heat is applied .and .the .black oil is introduced into thisoutside section. A thorough mixing of the high temperature and black oilstreams is accomplished in this outside section to produce a homogeneous.mixture and the commingled oils arevsubjectedto a period of soakingWithout the application of external heat to the coil. The mixture isthen returned to the furnace or heati'ngzone for completion of thecracking operation.

- In'one method of practicing the invention the high'temperature streamwhich is directed into the outside soaking section is first contactedwith a condensate stock or vaporizable oil and bottom burner I l.

the black oil is introduced into the resulting mixture in a subsequentportion of the outside soaking section, the black-oil mixture being thendelivered to a final section of the heating coil in the furnace.

For the purpose of more fully describing the invention reference is nowhad to the accompanying drawing which is a diagrammatic horizontal crosssection of an apparatus adapted for practicing the invention.

In the drawing a heating apparatus of the well-known de Florez type isillustrated. While the practice of the inventionis byno means restrictedto this type of furnace, nevertheless, the de l lorez method of heatingis particularly advantageous in the practice of the invention. Ii]represents the wall of a vertical furnace which may be suitably firedand provided with either down-draft or up-draft in the well known deFlorez manner. As illustrated, the furnace is of the up-draft type andis provided with a Vertically disposed tubes are arranged adjacent thewall ofthe furnace .so as to be, heated 'preponderantly by radiant heat.A primary'row of tubes I2 is connected by alternate top and bottomheaders .or return bends to provide for series flow through the tubes.The condensate stock isintroduced to the first tube of the series bymeans of an inlet pipe I}, A transfer line H conducts the oil from thelast tube ofthe row of tubes I! to an outside .row of tubes [5. Thetubes 15 aredisposed outside the furnace and are not subjected to anyexternal heating means. The tubes are provided with alternate top andbottom headers or return bends to provide for series flow through thetubes. A line It is provided for introducing a condensate orvaporizable'stock to the first tube of the outside row of soaking tubes.A line I] is provided for introducing the black oil or residual stock toone of the subsequent tubes in the row of soaking tubes IS. A transferline l8 serves to conduct theoil from the last tube of the row ofsoaking tubes l5 to the first tube of asecond or final series of tubesI9 disposed adjacent the furnace wall 10 and adapted to be heated pre:ponderantly by radiantheat. This row of tubes is connected by alternatetop and bottom headers to provide series flow through the rowof tubes.An outlet of transfer line 20 extends from the last row of tubes 19 to asuitable separator .(not shown) for separating the oracked products intovapors and residue.

In practicing theinvention the condensate stock" below 0.025%. The stockmay be a recycle stock obtained in the fractionation of the cracked Vapors or it may :be a straight-run or cracked stock which is subjected tosingle'pass cracking in the coil i i or it may consist of 'a'i'nixtureof straightrun and recycle stock. The oil -in transit throughthe tubesI2 is maintained under cracking conditions of temperature and pressuretoefiectthe desired conversion. It is desirable to heat the oil in thecoil l2 so that it is discharged fromthelast tube of the ,coil throughpipe l4 at a temperature; in excess of 900 F. and preferably attemperatures of theprder of 1000 or 1050 F. The pressurein the coil I2should ordinarily be in excess of about 200 lbs. and usually is of theorderof 400-800 lbs. The condensate introduced through line l6 iseitherrecycle stock or condens'ate from an extraneous source and isintrod'ucedat temperatures preferably of 500 F.-700 F. The usual methodof introducing the black oil through line I! is to charge a residualstock such as topped or reduced crude into a primary dephlegmator of thesystem and use the resultantmix'tureo'f 'unvaporized' charge and heavyre- 'fiux' condensate as'the stock which is injected through the line IT. some cases the topped bfi'educed crude is drawn from the crude stillsinaheatedcondition and passed directly through 'a'line l7 to t ereon l5.The black oil is preferably introduced at temperatures of about 600 F.b'rvo'mmor higher.

By reason of'the change of direction in the flow of oil back and forththrough the soaking tubes lf'a completelyhomogeneous mixture of theblack oil with'theprodu'cts from the heating coil- IZ'is obtained beforethe mixture is'passed t'o'the final heating coils 19 in the furnace.The. heating apparatus specifically described hereinis particularly'adapted for providing an even heat distribution throughout the furnaceso that the" furnace temperatures applied to the heating coil l2 mayapproximate the temperaturejapplied to the'heatin'g'coil l9. However,the heat densities applied to .the coil l9 will be lower thanfthsfapplied'to the coil 12, due to the higher temperatures 'of'the oil inthe coil 19. It is advantageous to apply lower heat densities to thefinalbank'of tubes in which the final cracking is takingplace 'f f In anexample of the invention cycle condensate is subjected to'crackingintheheating coil I 21 and is'pa'ssed through line 14 at a temperature ofl0'10 F. The cracked products are permitted to cool to a temperature 'of990 F. before introducing the black oil; The black oil is introduced ata temperature' of 700 F. and the mixture passes from the soaking andmixing tubes through the line lS at a temperature of 875F. The mixtureis raised 'in temperatures in transit through the tubes l9 and isdischarged therefrom at a temperature of920 F. p

In another exampleof thefinvention the cycle condensate'is'passed fromthe coil l2 through the transfer line J4 at a temperature of 1010" F.,Ia small portion of the cycle'condensate from the bubble tower isinjected through line I6 at a teni perature of 67 0 F. to thereby reducethe temperature of the cracked products in coil i5 to 960 F. The blackoil is introduced through line ll at a temperature of 700 F. and themixture is passed through line l8 at a temperature of 880 F. to thefinal heating bank it in which the temperature is raised to 930 F.

While we have described a particular embodiment of our invention forpurposes of illustration, it should be understood that variousmodifications and adaptations thereof which will be obvious to oneskilled in the art, may be made Within the spirit of th invention as setforth in the appended claims.

We claim:

1. In the cracking of hydrocarbon oils the process that comprisespassing a condensate stock through a heating coil in a heating zone,burning' fuel to generate heat for the heating zone and applying thegenerated heat to said heating coil to subject the oil stream to a highcracking temperature, discharging th heated oil stream from the heatingZone and passing it through a. confined passageway in a cooling zone tothereby effect a reduction in the temperature of the oil stream,introducing a black oil stock into the cooled stream, passing theresultant mixture through a confined passageway with successive changesin the direction 01 flow to thereby produce therein a homogeneousmixture 'while continuing the application of cooling to the confinedpassageway, passing the homogeneous mixture thence through a subsequentheating coil and applying generated heat thereto to raise t etemperature of the oil stream and subject it to further crackingtherein. I

2. 1n the cracking hydrocarbon oils, the

process that comprises passing a condensate stock through a, heatingcoil in a heating zone, burning fuel to generate radiant heat for theheating zone and applying resultant radiant heat to said heating 0011 tosubject the on stream to a high cracking temperature and subject it tocracking, discharging the heated oil stream from the heating zone andpassing it through a confined passageway in a cooling zone to therebyeffect areduction in the temperature of the oil stream, introducing ablack oil stock into the cooled stream, passing the resultant mixturethrough a confined passageway with successive changes in the directionof flow to thereby produce therein a homogeneous mixture whilecontinuing t e application of cooling to the confined passageway,directing the homogeneous mixture thenc through a subsequent heatingcoil disposed in the aforesaid heating zone and applying radiant heattoraise thetemperature thereof, and subjecting the oil to further crackingtherein.

:5. In the cracking oi hydrocarbon oils the process that comprisespassing a condensate stock through a heating coil in a heating zone,burning iue to generate heat for the heating zone and applying thegenerated heat to said heating coil to subject the oil stream to a highcracking temperature, discharging the heated oil stream from the heatingzone and passing it through a confined passageway in a cooling zone tothereby eifect a reduction in the temperature of the oil stream,introducing a relatively cool condensate oil into said confinedpassageway to lower the temperature of the oil stream flowing therein,introducing a black on stock into the cooled tream and passing theresultant mixture through a confined passageway with successive changesin the direction of flow to thereby produce therein a homogeneousmixture while continuing the application of cooling to the confinedpassageway, passing the homogeneous mixture thence through a subsequentheating coil and applying generated heat thereto to raise thetemperature of the stream and subject it to further cracking therein.

4. In the cracking of hydrocarbon oils the process that comprisespassing a condensate stock through a heating coil in a heating zone,burning fuel to generate heat for the heating zone and applying thegenerated heat to said heating coil to subject the oil stream to a highcracking temperature and efiect cracking, discharging the heated oilstream from the heating zone and passing it through a confinedpassageway in a cooling zone to thereby effect a reduction in thetemperature of the oil stream but not below a 20 temperature within thecracking range, introducing a black oil stock into the cooled stream,passing the resulting mixture through a confined passageway withsuccessive changes in the direction of flow to thereby produce therein ahomogeneous mixture While continuing the application of cooling to theconfined passageway to maintain the mixture flowing therein at atemperature below the maximum temperature in said heating coil but at atemperature within the cracking range so that cracking is continued intransit through said confined passageway, passing the homogeneousmixture thence through a subsequent heating coil and applying generatedheat thereto to raise the temperature of the oil stream and subject itto further cracking therein.

LUIS 1m FLOREZ. JAMES W. GRAY.

